1. Field of the Invention
The present invention relates to a communication apparatus and a communication system, and particularly to a communication apparatus and a communication system which can maintain an excellent quality of a wireless communication implemented by a first communication portion while ensuring a communication time for a wireless communication implemented by a second communication portion.
2. Description of Related Art
There is known a communication apparatus that simultaneously makes communications with a plurality of other communication apparatuses by respective wireless communication methods and by using a same frequency band. This communication apparatus suffers from a radio interference since the communications by the respective communication methods are made by using the same frequency band. The radio interference may degrade the qualities of the communications.
JP-A-2003-18170 (see paragraph [0017]) discloses a technique for inhibiting the radio interference so as to maintain excellent qualities of the communications. That is, according to this publication, while a communication apparatus (hereinafter referred to as “communication apparatus X”) is wirelessly communicating with a first other communication apparatus and a second other communication apparatus simultaneously, by means of a carrier wave of a first wireless channel and by means of a carrier wave of a second wireless channel, respectively, when one (hereinafter referred to as “communication apparatus Y”) of the first and second other communication apparatuses detects that the carrier of the communication between the communication apparatus X and the other (hereinafter referred to as “communication apparatus Z”) of the first and second other communication apparatuses uses a same wireless channel as used by the carrier of the communication between the communication apparatus X and itself (i.e., the communication apparatus Y) and notifies this fact to the communication apparatus X, the communication apparatus X ceases the communication with the communication apparatus Z.
According to this technique, regardless of whether the communication between the communication apparatuses X and Z is still desired or not, the communication therebetween is ceased when the above-described condition is satisfied.
On the other hand, if the communication between the communication apparatuses X and Z is not ceased, a radio interference occurs. In this case, a problem arises, which will be described with reference to FIG. 11 schematically illustrating a wireless communication environment of the communication apparatus X.
That is, the communication apparatus X has a housing that accommodates (i) a digital cordless communication portion 101 as a wireless communication module used when the communication apparatus X functions as a base unit of a digital cordless telephone system to wirelessly communicate with a cordless handset Y, and (ii) a wireless LAN communication portion 102 as a communication module used when the communication apparatus X wirelessly communicates with a PC 105 via an access point Z.
When the communication apparatus X is wirelessly communicating with both the cordless handset Y and the PC 105, the digital cordless communication portion 101 suffers from a radio interference K1 from the access point Z and a radio interference K3 from the wireless LAN communication portion 102. On the other hand, the cordless handset Y suffers from a radio interference K2 from the access point Z and a radio interference K4 from the wireless LAN communication portion 102.
Generally, the digital cordless communication portion 101 more seriously suffers from radio interference than the cordless handset Y does, for the following reason.
That is, the digital cordless communication portion 101 is disposed in the same housing as the wireless LAN communication portion 102 is, and generally a distance L1 between the digital cordless communication portion 101 and the wireless LAN communication portion 102 is considerably smaller than a distance L2 between the digital cordless communication portion 101 and the cordless handset Y and a distance L3 between the wireless LAN communication portion 102 and the access point Z. Hence, the radio interference K3 from the wireless LAN communication portion 102 that the digital cordless communication portion 101 suffers from is relatively strong. Thus, the digital cordless communication portion 101 more tends to suffer from radio interference than the cordless handset Y does.
Hence, while the digital cordless communication portion 101 of the communication apparatus X and the cordless handset Y wirelessly communicate with each other, a communication D2 from the cordless handset Y to the digital cordless communication portion 101 is more susceptible to radio interference than a communication D1 from the digital cordless communication portion 101 to the cordless handset Y. Thus, the quality of the communication D2 from the cordless handset Y to the digital cordless communication portion 101 tends to be relatively poor in comparison with that of the communication D1 from the digital cordless communication portion 101 to the cordless handset Y.